Pressure-induced Raman spectral changes of N,N,diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate

We have measured Raman spectral changes in one of the aliphatic series of ionic liquids, N,N,diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF4], under high pressure. Although the [DEME] cation has mainly two stable conformers of TG+-tg+t and TG+-g+g-t in the liquid state, the population of the minor conformer, i.e. TG+-g+g-t, decreases with increasing pressure. The difference in the partial molar volume between the two conformers was determined from the pressure dependence of the relative Raman intensity ratio.